Submersible pumps are in common use, usually employing an electric motor contained within a housing and having a shaft incorporated through glands to an impeller. Pumps which are in continuous use such as suds pumps usually rely upon heat transfer from a cool liquid, through the walls of the motor housing, to cool the motor, but in applications such as evaporative coolers submersible pumps are seldom used, since transfer of heat from the motor is difficult to achieve because the motor is fully enclosed but not immersed, and a deleterious temperature rise can occur within the motor housing which can result in casing damage and motor burn out on hot days. It is an object of this invention to provide a pump wherein likelihood of such damage is greatly reduced.